Adventurer's Armory was a product completely different than anything that had appeared in Pathfinder's Player Companion line up to that point. Whereas previous entries in the series has been about specific regions or races and contained far more "fluff" than "crunch", the Adventurer's Armory was almost *all* crunch. Full of new equipment, weapons, services, and more, the book drastically expanded the amount of stuff that PCs could spend their hard-earned (or stolen) gold on. It's probably the reason it's the most popular Player's Companion, and (I think) the only one to ever receive a second printing. Indeed, its continuing popularity is such that it's led to an announced Adventurer's Armory 2 later in 2017, which means Adventurer's Armory is the first product in the line to receive a direct sequel.
The inside front- and back- covers are tables providing statistics for the new weapons introduced in the book. The interior is then divided into six sections.
The first section, and by far the longest at 20 pages, is "Weapons, Armor, and Adventuring Gear." This section is exactly what it sounds like. There are 45(!) new weapons, including some classics from previous editions of D&D like the bardiche and lasso, as well as many I've never seen before, like the meteor hammer, groaning bullets, and syringe spear. One new shield (a "madu") and one new armor (parade armor) are introduced. The section then details dozens of new pieces of miscellaneous adventuring gear, including some that have become extremely common in groups I've played in, such as masterwork backpacks and skeleton keys. Players interested in alchemy will be happy, as a couple of dozen of substances are introduced, including everything from sneezing powder to bladeguard (for rust monster protection!). There are then 24 new tool and skill kits, such as portable alchemist's labs, a stretcher, and a portable altar. Some fun new clothing options are introduced such as tear-away clothing, as well as some eminently sensible choices like hot weather outfits. Foods and drinks receive descriptions and prices: everything from coffee and tea to Linnorm mead and Mwangi coffee. Want an animal as a pet or companion? Dogs, dire rats, stirges (!), and more are priced. Last, there's a handful of entertainment items (like loaded dice and marked cards) and herbal items. Perhaps disturbingly, there's even an entry on purchasing different types of slaves.
The second section, "Combat", comes in at two pages and introduces the concept of equipment tricks. Basically, by taking the Equipment Trick feat, a character can learn to do special things with one particular type of equipment like a rope or a shield. This section details Heavy Blade Scabbard tricks (like flipping a disarmed weapon into an empty scabbard) and Shield tricks (like throwing your shield to bounce off stuff like Captain America). I've never used equipment tricks in a game, but some of them actually look pretty fun.
A two-page "Faith" section introduces several new items for divine casters, most of them relating to a cleric's ability to channel energy.
The "Magic" section, also two pages long, focuses on the concept of Alchemical Power Components: basically, using an alchemical item as an added component when casting a spell to boost its power. Using a flask of alchemist's fire when casting burning hands, for example, means that one target that fails its save catches on fire. Some of the boosts are quite minor, while others could be extremely useful in the right circumstances, like using a tanglefoot back to allow your black tentacles to reroll grapple checks.
The "Persona" section details an NPC alchemist-for-hire named Arayam Bismut. Bismut is given an intriguing backstory involving a family curse and could make a decent cohort. A major thing to keep in mind, however, is that this product came out (I assume) before the Alchemist class became part of the game, so Bismut is statted out as simply a Level 6 Expert.
The final section, oddly labelled "Social", introduces the concept of Equipment Traits: things like having an heirloom weapon or being more skilled than most at using improvised weapons. Two new feats (Sly Draw and Splash Weapon Mastery) aid rogues who want to feint and bomb-hurlers respectively.
It's hard to imagine a player flipping through this book and *not* finding something useful for their character. The options provided expand, quite usefully, the understandably limited selection in the Core Rulebook. On the other hand, as everything apart from the NPC is open content, these items could just as easily be found in the PRD or PFSRD. Still, I'm confident the upcoming sequel to this book will also sell like hotcakes.
NOTE: The first printing of this book was apparently full of typos and errors. I'm operating off the second printing, and most of the problems seem to have been fixed.